The printheads used by inkjet printers traditionally traverse back and forth within the printer as a page is fed past the printhead. To increase printing speed, pagewidth printheads have been developed so that the printhead does not need to traverse across the page.
For a number of reasons, it is relatively expensive to produce pagewidth printheads in a unitary form. Therefore, to minimize costs it is preferable to produce a modular pagewidth printhead made up of a series of printhead modules.
It is necessary to align each module so that the printing from one module precisely abuts the printing from the adjacent modules. For most types of printing, it is sufficient to electronically align the modules. This is done by configuring the modules such that they slightly overlap with each other, and then digitally adjusting the printing from each module for a smooth transition of the print data.
Unfortunately, this requires complex manipulation of the print data allocated to the respective modules. The digital controller for the printer needs to be relatively powerful to accommodate this and the associated costs can be prohibitive for the SOHO (small office/home office) market.
Accordingly, the present invention provides a modular printhead for a digital printer, the modular printhead including:
a support frame and a plurality of printhead modules, the frame having a plurality of mounting sites for mounting respective printhead modules to the frame; wherein,
at least one of the mounting sites has an adjustment mechanism for reducing input movements to effect minute adjustments of the position of the printhead module with respect to the frame.
Preferably, the adjustment mechanism uses a system of levers and pivots for geared reduction of the input movements to minute adjustments of the printhead module relative to the frame. In a further preferred form, the ratio of input movement to the resultant adjustment is at least 500 to 1.
In a particularly preferred form, the movement of the printhead module relative to the frame is less than 100 xcexcm.
In some embodiments, the adjustment mechanism includes an input lever fulcrumed against the support frame for acting on a module engagement plate, the module engagement plate being connected to the support frame by hinged link arms such that the resultant movement of the plate is substantially linear. Preferably, the movement of the input lever is substantially normal to the resultant movement of the engagement plate. In a further preferred form, the input lever for each of the adjustment mechanisms is actuated by a respective grub screw threadedly engaged with the support frame. Conveniently, the ratio of axial movement of the grub screw to the movement of the plate is about 1000 to 1.
Conveniently, the adjustment mechanism is integrally formed with the frame wherein the fulcrum and hinged connections are formed by localized necks in the frame material.